This invention relates to the measurement of gas characteristics through the use of a probe comprising a solid electrolyte which is in contact on one side or face with a reference gas such as the ambient atmosphere and is in contact on the opposing side or face with a hot gas whose characteristics are to be measured. In such a probe, a voltage is generated between the two sides or faces of the solid electrolyte, the magnitude of the voltage being dependent upon the temperature of the electrolyte and on the ratio of the oxygen partial pressure on opposing sides or faces of the electrolyte. This principle has been used in the past to measure the oxygen partial pressure of hot furnace gases with various different oxygen sensors, such as disclosed in U.S. Pat. Nos. 3,454,486; 3,546,086 and 3,596,345 and British Pat. No. 1,296,995.
Although the principle of operation of the abovenoted type of oxygen sensors is quite simple, the utilization of such oxygen sensors in industrial applications has been limited in the past due to several practical problems. First, the solid electrolyte, which is a ceramic material, is hard and brittle and is thus very susceptible to thermal shock and/or mechanical damage. Another problem has been the detachment of the electrode from the surface of the electrolyte due to corrosion of the electrodes. The latter problem occurs even when the electrodes are made of a noble metal, such as platinum. For example, platinum reacts at high temperatures and low oxygen pressures with stabilized zirconia electrolyte material, which is commonly used in this type of oxygen sensor to form ZrPt.sub.3. The reaction product is in the form of fragments or dust which drops away from the electrode, thus reducing the thickness thereof and eventually breaking the electrical contact between the electrode and the electrolyte or loosening the electrode sufficiently in its mounting to allow it to be blown away by the gas stream under measurement. For the above reasons, the useful working life of the above-noted type of oxygen sensor has been limited in the past and has limited their potential range of application.